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Patented Aug. 9, |898.

J.F.KELLY.

LIGHTNING ARRESTER.

(Application filed Dec. 16, 1895.)

2 Sheets-Sheet l.

(No Model.)

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No. 608,685. Patented Aug. 9, |898. J. F. KELLY.

LIGHTNING ARRESTER.

(Application filed Dec. 16, 1895.)

(No Model.) 2 Sheets-Sheet 2.

Fig. 5.

WITNESSES: v VENTOR 7M @if UNITED STATES PATENT OFFICE.

JOHN Fa KELLY, OF IITTSFIELD, MASSACHUSETS, ASSIGNOR OF ONE-HALF TOCUMMINGS C. CHESNEY, OF SAME PLACE.

LIGHTNING-ARRESTER.

SPECIFICATION forming part of Letters Patent No. 608,685, dated August9, 1898.

Application tiled December 16, 1895. Serial No. 572,228. (No model.)

To @ZZ whom zit may concern:

De it known that I, JOHN F. KELLY, a citizen of the United States,residing at Pittsfield, in the county of Berkshire and State ofMassachusetts, have invented a new and useful Lightning-Arrester, ot'which the following is a speciiication.

My invention belongs to that class of instruments used in electricalsystems, whether for alterna-ting' or continuous currents, forpermitting the passage to the earth of any currents of abnormally highdifference of potential which may be dueto static discharges, such aslightning or other causes, and which if not provided for are liable toinjure the system or parts thereof. Such instruments are commonly knownas lightning-arresters.

My invention has for its object to provide an arrester which, whileoffering practically infinite resistance to ordinary electromotiveforces, shall be readily permeable to hightension static discharges, andincidentally in my preferred form to provide an arrester which is initself at the same time a safetyfuse. I attain these objects by the useof a device hereinafter described, reference being had to theaccompanying drawings,in which- Figure l represent-s a perspective Viewof a device embodying my invention. Fig. 2 represents a side view of thesame with the parts cutaway so as to show the details more clearly, andFig. 3 represents the generator and line of a system of electricaldistribution with my arrester applied.

To lightning-arresters such as are at present used there are variousobjections. For instance, they either oifer an objectionably highresistance to the passage of the current of abnormallyhigh difference ofpotential or an objectionably low resistance to the passage of thenormal current or are too costly or too bulky for ordinary use. In thefirst case they cannot be relied upon to operate in all cases ofnecessity, In the second case if they do operate when needed the normalcurrent will follow the abnormal discharge and continue to follow ituntil interrupted by some outside means, thereby becoming in itself asource of danger. My invention avoids all these objections, being ofreasonable cost and of small bulk and eifel-ing a resistance to staticdischarges and the like neither too high, so

to impair its usefulness as an arrester, nor too low, so as to interferewith the system under normal conditions. Aside from these 55 advantagesthe particular device hereinafter shown and described as being anembodiment of my invention in its preferred form may act as asafety-fuse, so that if the normal current should follow the staticdischarge the circuit would be automatically opened.

The drawings represent an arrester enibodying my invention in itspreferred form. This device consists of a non-conducting body orcylinder C, mounted upon a suitable support S by bands T T andcontaining a series of conducting or semieonducting pieces I I in badelectrical contact with one another. The cylinder C has metallic endpieces or caps D E, having binding-posts F G, to which the conductors LL to the line and to the earth are connected, respectively. The cap Dhas a pressure-screw I), which bears upon one end of the series I I, soas to insure lgoed contact between the ends of the series and the caps DE. By using a sufficient number of pieces in the series the bad contactspractically open the circuit for ordinary electronictive forces and yetare very readily traversed by high-tension discharges. One of thesimplest ways of making the series of conducting or semiconductingbodies is to form a column of lead pellets, such as shot more or lessoxidized. I have found that an arrester constructed with aneighteen-inch column of oxidized shot, as above described, the shotbeing about eighteen-hundredths of an inch in diaineter and onlyslightly and superficially oxidized and being arranged in a singlescries, as shown in the drawings, will withstand with safety twothousand volts pressure and yet at the same time be easily traversed bya spari; from a small Holtz machine. One great dilticulty with thepresent type of lightningarresters of this class seems te be that theyoffer toc great a resistance to the q uiclr pas-- sage therethrough of acurrent of abnormally high tension and toe low a resistance to preventthe passage of an appreciable amount of current at normal tension, as aconsequence of which latter some of the normal current is certain toleak away. My device offers substantially no passage for currents ofnormal tension, but a comparatively low resistance to currents of veryhigh or abnormal tension. When lightning strikes the line, the enormoustension of the current resulting therefrom changes the condition of theparticles and reduces the resistance of the arrester, so that the chargepasses off at once.

In Fig. 3 I have shown my arrester in connection with a portion of asystem in which it is so located as to protect a generator K. Thearrester consists of the device described above and is connected to theline in the same manner as the ordinary spark gap arresterthat is, theline is directly connected to one terminal by the conductor L, While aconductor L, leading to the earth, is connected to the other.

Although it is not necessary to use pellets of lead or a similar fusiblemetal in making up the series I I in arresters embodying my invention,broadly considered, their use presents a distinct advantage-namely, thatarresters when so constructed, if arranged with the column in a verticalposition, will themselves act perfectly as safety-fuses, since when suchan arrester is so used, if the current should follow the path of thelightning discharge, the pieces making up the series will fuse and falltogether, thus opening the circuit. The arrester as thus constructed isan almost perfect safeguard against static discharges reaching themachine or instrument to be protected and also against theshortcircuiting of such a machine or instrument itself when it is acurrent-generator. The arrester is connected with the system in theusual manner, so as to form a shunt to the earth for the staticdischarge. Y

What I claim as my invention, and desire to secure by Letters Patent,is-

1. A lightning-arrester consisting of a column of conducting orsemiconducting bodies in bad contact With one another, as a Wholepractically nonconducting under ordinary electric stress, but under highstresses conducting, in combination with suitable terminals for theline, in contact with the column respectively, substantially asdescribed.

2. A lightning-arrester consisting of a nonconducting containing vessel,in combination With a column of conducting or semiconducting bodies inbad contact with one another, Within said vessel, and suitable terminalsin contact With the ends of the column respectively, substantially asdescribed.

3. A lightning-arrester consisting of a column of fusible conducting orsemiconducting bodies held in position in bad contact with one another,in combination With suitable terminals in contact With the ends of thecolumn respectively, substantially as described.

4. A lightning-arrester consisting of a column of pieces of fusiblemetal partially oxidized, held in position in combination Withsuitableterminals in contact with the ends of the column respectively,substantially as described.

In testimony whereof I have hereunto set my hand this 11th day ofDecember, 1895.

JOHN F. KELLY.

Vitnesses:

C. C. CHEsNEY, A. C. BUNKER.

